AT Command Set
MC35_ATC_01_V04.00 Page 92 of 238 02.04.2002
turns to the AT command mode.
3. There are various options to switch from data mode to command m ode:
a) Escape sequence +++
b) Circuit 108/2 (DTR) changes from ON to OFF, reaction depends on
command at&d (caution if AT&D0: TA ignores status on DTR).
c) The message Modem Status Command (MSC) for control c hannel is
defined by the multiplexer protocol GSM07.10. MSC conveys V.24
signals. Bit 3 of Control Signal Octet is DTR, reaction depends on
command at&d (caution if AT&D0: TA ignores status on DTR).
4. The parameter maximum frame size (N1) of AT+CMUX in GSM07.07 is
fixed to 97 and cannot be changed. All other parameters are not avail-
able.
5. Multiplex mode can be terminated by AT^SM SO (,AT^SMSO Switch off
mobile station" pg. 191). It has to be reestablished after power-on.
4.28.1 Restricted use of AT commands in Multiplex mode
In Multiplex mode, the operation of several AT commands varies f rom the normal mode. This chapter
summarizes the concerned commands. For general rules and restricti ons to be considered in Multiplex
mode please refer to [5].
Data, fax and GPRS calls can only be set up on logical channel 1. Due to this restriction, AT com-
mands have a different behaviour on channels 2+3 compared to channel 1. Several commands are
not available, others return different responses. These commands are liste d in the table below:
Table 6: Availability of AT commands on virtual channels
Command Behaviour on channel 1 Differences on channel 2+3
+++ as described not usable
ATE as described as described
AT+CBST as described not usable
AT+CR as described not usable
AT+CRLP as described not usable
AT+CG... (GPRS commands) as described usage not recommended 2)
AT+F.... (Fax commands) as described not usable
AT&C as described not usable
AT&D as described not usable
AT&F as described data call parameters not changed
S3, S4 not changed
AT&S as described not usable
AT&V as described data call parameters not displayed
ATA as described no data calls
ATD as described no data calls
ATDI<n> as described not usable
ATO as described not usable
ATS0 1)as described not usable
ATS3 1)as described as described